<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>图片放大效果</title>
<style type="text/css">
#div1 { width: 200px; height: 200px; padding: 5px; border: 1px solid #ccc; position: relative; }
#div1 .small_pic { width: 200px; height: 200px; background: #eee; position: relative; }
#div1 .float_layer { width: 50px; height: 50px; border: 1px solid #000; background: #fff; filter: alpha(opacity: 30); opacity: 0.3; position: absolute; top: 0; left: 0; display:none; }
#div1 .mark {width:100%; height:100%; position:absolute; z-index:2; left:0px; top:0px; background:red; filter:alpha(opacity:0); opacity:0;}
#div1 .big_pic { position: absolute; top: -1px; left: 215px; width:250px; height:250px; overflow:hidden; border:2px solid #CCC; display:none; }
#div1 .big_pic img { position:absolute; top: -30px; left: -80px; }
</style>
<script type="text/javascript">
function getByClass(oParent, sClass)
{
 var aEle=oParent.getElementsByTagName('*');
 var aTmp=[];
 var i=0;
 
 for(i=0;i<aEle.length;i++)
 {
  if(aEle[i].className==sClass)
  {
   aTmp.push(aEle[i]);
  }
 }
 
 return aTmp;
}
window.onload=function ()
{
 var oDiv=document.getElementById('div1');
 var oMark=getByClass(oDiv, 'mark')[0];
 var oFloat=getByClass(oDiv, 'float_layer')[0];
 var oBig=getByClass(oDiv, 'big_pic')[0];
 var oSmall=getByClass(oDiv, 'small_pic')[0];
 var oImg=oBig.getElementsByTagName('img')[0];
 
 oMark.onmouseover=function ()
 {
  oFloat.style.display='block';
  oBig.style.display='block';
 };
 
 oMark.onmouseout=function ()
 {
  oFloat.style.display='none';
  oBig.style.display='none';
 };
 
 oMark.onmousemove=function (ev)
 {
  var oEvent=ev||event;
  
  var l=oEvent.clientX-oDiv.offsetLeft-oSmall.offsetLeft-oFloat.offsetWidth/2;
  var t=oEvent.clientY-oDiv.offsetTop-oSmall.offsetTop-oFloat.offsetHeight/2;
  
  if(l<0)
  {
   l=0;
  }
  else if(l>oMark.offsetWidth-oFloat.offsetWidth)
  {
   l=oMark.offsetWidth-oFloat.offsetWidth;
  }
  
  if(t<0)
  {
   t=0;
  }
  else if(t>oMark.offsetHeight-oFloat.offsetHeight)
  {
   t=oMark.offsetHeight-oFloat.offsetHeight;
  }
  
  oFloat.style.left=l+'px';
  oFloat.style.top=t+'px';
  
  var percentX=l/(oMark.offsetWidth-oFloat.offsetWidth);
  var percentY=t/(oMark.offsetHeight-oFloat.offsetHeight);
  
  oImg.style.left=-percentX*(oImg.offsetWidth-oBig.offsetWidth)+'px';
  oImg.style.top=-percentY*(oImg.offsetHeight-oBig.offsetHeight)+'px';
 };
};
</script>
</head>
<body>
<div id="div1">
    <div class="small_pic">
  <span class="mark"></span>
        <span class="float_layer"></span>
        <img src="http://www.miaov.com/miaov_demo/hand_lens/images/small.png" alt="smark" />
    </div>
    <div class="big_pic">
  <img src="http://www.miaov.com/miaov_demo/hand_lens/images/big.png" alt="big"  />
 </div>
</div>
</body>
</html>